Please excuse me if this is a repeat. The original post did not appear immediately as it usually does.

I am trying to run a Monte Carlo simulation to compare each quantile of a randomly generated set of attributes to the resulting quantile of a predicted class value. So far, it has worked for several learners, but not for the regression tree learner. I use a data file with at least one continuous attribute column and exactly one continuous class column to initialize the learner as follows:

I notice to have the learner predict from a set of attributes, it needs a placeholder for class value. After experimentation I learned it doesn't matter what the placeholder is, so I added "" as follows: